Stiffness reduction in soft Chicago clay during deep urban excavations

摘要

The nonlinearity and anisotropy are two key issues in evaluating the soil stiffness for the precisernprediction of the displacement. Recent studies on the stress-strain behavior of Chicago clay, especially focused onrnthe responses at small-strains, reveal the pattern of nonlinear stiffness degradation as the clay is stressed. Herein,rnwe attempt to apply these observational responses of Chicago clay to an excavation problem. The finite elementrnsimulation of the excavation in the downtown Chicago area was conducted. At some observation locations, thernsimulations yield typical stress paths. Changes in nonlinearity and anisotropy were discussed by comparingrncomputed and experimental stress paths. Even in the first few excavations, the reduction of shear stiffness couldrnbe significant in soft Chicago clay.